A plasma processing apparatus, for performing a plasma process on a semiconductor wafer (hereinafter, referred to simply as “wafer”) as a substrate, includes a chamber accommodating therein a wafer, an electrode disposed in the chamber and a shower head for supplying a processing gas into the chamber and the like. The plasma processing apparatus further includes various sensors for measuring output values of the components as processing parameters, respectively. The plasma processing apparatus controls the components based on a processing condition (recipe) applied thereto to perform various plasma processes on the wafer. At that time, in the plasma processing apparatus, the output values of the controlled components are measured by the sensors as the processing parameters, which are recorded as log data.
Typically, in case a plasma processing apparatus (hereinafter, referred to as “target apparatus”) performs a specific plasma process that has not been executed by the target apparatus, the target apparatus may be operated under a processing condition (hereinafter, referred to as “applied processing condition”) applied in another plasma processing apparatus (hereinafter, referred to as “reference apparatus”) which executed the specific plasma process. However, since the plasma process is a delicate process, even though the target apparatus performs the plasma process on the wafer under the applied processing condition, the plasma process may not be normally performed on the wafer due to a difference between the reference apparatus and the target apparatus. Accordingly, it is required to determine whether or not the target apparatus normally performs the plasma process on the wafer.
It is determined whether or not the target apparatus performs normally the plasma process on the wafer under the applied processing condition by comparing processing result data for a plurality of wafers that were normally processed under the applied processing condition in the reference apparatus with processing result data for a plurality of wafers that were processed under the same applied processing condition in the target apparatus. Specifically, in case the processing result data in the reference apparatus and those in the target apparatus substantially coincide with each other, it is determined that the wafers were normally processed. On the other hand, in case the processing result data in the reference apparatus and those in the target apparatus do not coincide with each other, it is determined that the wafers were not normally processed.
Further, processing parameter values (hereinafter, referred to as “normal processing parameter values”), measured in the target apparatus when the processing result data in the reference apparatus and those in the target apparatus substantially coincide with each other, are taken as references for determining whether or not the wafers are normally processed in the target apparatus (operation status of the target apparatus). For example, in a subsequent plasma process, when the processing parameter values measured in the target apparatus substantially coincide with the normal processing parameter values, it can be determined that wafers are normally processed (normal operation status), whereas when the measured processing parameter values do not coincide with the normal processing parameter values, it can be determined that wafers are not normally processed (abnormal operation status). Moreover, for accurate determination, a number of normal processing parameter values are required.
Meanwhile, there are various items of processing result data for the wafer (e.g., width or depth of a trench formed in the wafer) and various kinds of the processing parameter values (e.g., a wall temperature of the chamber and a voltage applied to the electrode), so that in comparing the processing result data in the reference apparatus with those in the target apparatus and comparing the measured processing parameter values with the normal processing parameter values, a multivariate analysis, particularly a principal component analysis, is widely used. By using the principal component analysis, the processing result data and/or the processing parameter values including a number of variables (items and kinds) can be converted into data including, e.g., one or two variables, thus making the aforementioned data comparisons easy and understandable.
As an approach using the principal component analysis, there has been known a method for evaluating an operation status of a semiconductor manufacturing apparatus (plasma processing apparatus) by executing a principal component analysis for a plurality of data monitored to calculate principal component values (the first and the second principal component value) and monitoring the principal component values in a sequence of time (see, e.g., Japanese Patent Laid-open Publication No. 2004-47885 and the corresponding U.S. patent application Publication No. 2004/0049898).
However, in order to make it possible to determine whether or not the wafers are normally processed under the applied processing condition in the target apparatus (operation status of the target apparatus), there are required processing result data for a number of wafers and many normal processing parameter values in the target apparatus. Accordingly, for determining the operation status of the target apparatus, the target apparatus should perform the plasma process under the applied processing condition in advance.